Tim Tebow's Fiancee's Sister Dies Suddenly At 13 From A Rare Condition

From Women's Health

• Tim Tebow's fiancee, Demi-Leigh Nel-Peters, announced on Instagram that her 13-year-old sister, Franje, died on May 4.

• Franje had a rare condition called cerebellar agenesis, in which the brain develops without a cerebellum.

• The cerebellum controls motor function as well as memory and learning.

It's a sad day for former footballer Tim Tebow and his fiancee, Demi-Leigh Nel-Peters: According to an Instagram post from the South African beauty queen, her 13-year-old sister, Franje, died on May 4.

"My little Princess, Angel on Earth, biggest joy and baby sister, Franje, passed away earlier today," Demi-Leigh wrote in the caption. "Our hearts are aching beyond measure but I am grateful knowing she’s forever relieved of the pain she experienced on earth. She’s laughing, running and playing in heaven just like we always hoped she would on earth."

It was Franje who helped bring Demi-Leigh and Tim together in the first place. Franje was born with a condition called cerebellar agenesis and was invited to a celebration sponsored by the Tim Tebow Foundation.

"[Demi-Leigh's] sister has special needs, so we invited them to Night to Shine in South Africa," Tim explained to Kathie Lee Gifford and Hoda Kotb during an appearance on Today. "We kind of met and started talking through that and haven't stopped."

Tim, who proposed to Demi-Leigh in January, also posted a heartfelt remembrance of Franje, writing, "Our loss but heavens gain. So grateful for the hope we have of being reunited with the ones we love through our Heavenly Father. Mr & Mrs Peters and @demileighnp we are praying for you and love you so much."

What is cerebellar agenesis?

According to the National Organization for Rare Diseases (NORD), cerebellar agenesis is a condition in which the brain develops without a cerebellum. The cerebellum not only controls muscular activity (like movement of the muscles, the trunk and limbs, the tongue, and the eye muscles) but also plays a part in "learning, memory, language, and behavior," per the NORD.

Experts say there isn't one uniform cause of the condition-but it is often found in premature babies with a very low birth weight. Cerebellar agenesis can also be acquired through "cerebellar destruction caused by hemorrhage, lack of or diminished blood flow, or other factors," per the NORD.

Symptoms also vary and can be mild to severe and often include impaired motor function, delayed walking, difficulty speaking, and rapid/involuntary eye movements. While cerebellar agenesis tends to affect both males and females at similar rates, it isn't currently known how many people suffer from cerebellar agenesis. There's also no cure for cerebellar agenesis, but treatment can help specific symptoms of individuals with the condition.

We'll be keeping Demi-Leigh and Tim in our thoughts.

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